Schools are being sold software to monitor pupils' internet activity for extremism-related language such as "jihadi bride" and "YODO", short for you only die once.
Several companies are producing "anti-radicalisation" software to monitor pupils' internet activity ahead of the introduction of a legal requirement on schools to consider issues of terrorism and extremism among children.
Under the Counter-terrorism and Security Act 2015, which comes into force on 1 July, there is a requirement that schools "have due regard to the need to prevent pupils being drawn into terrorism".
One company, Impero , has launched a pilot of its software in 16 locations in the UK as well as five in the US. Teachers can store screenshots of anything of concern that is flagged up by the software. Other companies offering anti-radicalisation software products to schools include Future Digital and Serurus.
Impero has produced a glossary of trigger words such as "jihobbyist" (someone who sympathises with jihadi organisations but is not an active member) and "Message to America" (an Islamic State propaganda video series).
Schools involved with the Impero pilot already have contracts to buy or rent other software from the company, and are trialling the anti-radicalisation software at no extra charge. They are in areas including London, County Durham, Essex, Leicestershire, Warwickshire, Yorkshire and Staffordshire.
A spokeswoman for Impero said: "The Counter-terrorism and Security Act places a duty on schools to prevent people from being drawn into terrorism. Since the introduction of the act at the beginning of the year we have had a lot of schools approach us requesting a keyword-detection policy focused on radicalisation.
"The system may help teachers confirm identification of vulnerable children, or act as an early warning system to help identify children that may be at risk in future. It also provides evidence for teachers and child protection officers to use in order to intervene and support a child in a timely and appropriate manner.
"It is not about criminalising children, it is about helping schools spot the early warning signs so that risk in relation to an individual can be assessed and measured, and counter-narratives and support can be put in place to help educate children before they potentially become victims of radicalisation."
Different schools are interpreting the anti-radicalisation clause in the new counter-terrorism legislation in different ways. Headteachers interviewed by the Guardian said it was a very difficult issue for schools to get involved with.
Some schools are simply signalling that they are aware of the requirement to take the issue into account, while others are being more proactive. One school is east London is offering workshops on spotting signs of radicalisation.
Monega primary school in Newham has invited parents of children as young as four to a workshop on 26 June. The invitation states: "Come and join us for this session led by a social worker on how to prevent and detect radicalisation. All parents are welcome."
Yahya Birt, a Muslim academic specialising in British Islam, tweeted about the four-year-olds potentially being monitored for radicalisation: "They're pre-lingual, let alone pre-political. It's bonkers."
Last month there was controversy over a questionnaire circulated to pupils in five primary schools in Waltham Forest, another east London borough with a large Muslim population.
The questionnaire asked pupils leading questions about their views and beliefs including whether or not they would marry someone from a different religion, whether they would be prepared to hurt someone who made fun of their race or religion and whether they felt God had a purpose for them.
Waltham Forest council later said the questionnaires would be withdrawn. It said they had been produced by the behavioural insights team, also known as the "nudge unit", which started life inside 10 Downing Street and is partly government-owned.
An internal memo circulated to directors of children's services by the director of the Department for Education's due diligence and counter-extremism group states that in the wake of the three British Muslim teenagers going to Syria, schools are being offered more support in tackling extremism, including a dedicated helpline for teachers.
The department is carrying out a review of schools where there is evidence of pupils having links to people who may have travelled to Syria.
Birt tweeted : "This policy covers about 800,000 Muslims who are under-18 when maybe a couple of dozen of them are with Isis, it's a sledgehammer for a walnut."
Bill Bolloten, an education consultant who provides training to schools in this area, said: "There are growing concerns that many schools are failing to understand what is required under the new act. The prevent duty requires them to respond in ways that are proportionate and appropriate, based on an assessment of genuine risks that children might face in relation to extremism.
"Workshops for parents on extremism, as well as other activities such as radicalisation questionnaires for children and software that spies on pupils' internet activity in school, are based on the discredited idea that there are signs of extremism that can be detected in young children.
"These actions are alarming many parents and may compound a growing climate of mistrust. Schools should reflect and reconsider if these approaches are potentially counter-productive and might damage relationships with the communities they serve."
Impero glossary of key words and phrases that its software will flag up:
Jihadi bride: A woman convinced that it is her Islamic duty to travel to join a jihadi organisation such as Isis and marry one of its fighters. Searching for this term may indicate vulnerability to radicalisation or support for Islamist extremism.
John Cantlie: British journalist kidnapped and held hostage by Isis since 2012. He appears in several Isis propaganda videos.
War on Islam: Phrase often used by Islamists and jihadis to perpetuate the narrative that the west is at war with all Muslims, which is crucial to their radicalisation and recruitment aims.
Jihobbyist: Someone who sympathises or supports jihadist organisations but does not commit the offence of becoming an active member. Searching for this term may indicate support for jihadism.
Pogrom: An organised massacre or persecution of an ethnic or religious group, particularly Jews. Searching for this term may indicate support for far-right extremism.
YODO: Acronym for "you only die once", a jihadi parody of YOLO. Used to promote suicide bombings and recruitment to Isis.
Storm Front: White supremacist neo-nazi organisation.
Kuffs: Arabic term for infidel, hate speech used by Islamists to denote non-Muslims.
Message to America: Isis propaganda video series featuring beheadings of western hostages and threats to kill more.